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County by County, Young People Prove Pivotal in Iowa Caucus

Our exclusive analysis finds that Bernie Sanders and Elizabeth Warren performed best in Iowa counties with a high concentration of youth.

One controversial week after Iowans caucused for their preferred Democratic candidates, no winner has been officially declared in the nation’s first nominating contest. Senator Bernie Sanders appears to have won the most votes, while former Mayor Pete Buttigieg is ahead by just one-tenth of a percentage point in the “state delegate equivalents” count and is currently projected to receive the most national delegates. While the Iowa Democratic Party said it will launch a recanvass of results before certifying a winner, it’s clear that Sanders and Buttigieg had strong nights that gave a boost to their campaigns.

As we found in our initial analysis of the youth vote in Iowa—where young people made up 24% of all caucusgoers and nearly half supported Sanders—youth had a decisive impact on the caucuses. This new, county-by-county analysis of the youth vote highlights just how influential young caucusgoers were to the fortunes of the candidates. As one might expect, given his overall dominance among young voters, Iowa counties with a high proportion of youth strongly boosted Sanders’ (and, though somewhat less, Senator Elizabeth Warren’s) performance in the state, while hindering former Vice President Joe Biden, who finished fourth in the Iowa caucuses.

Youth-Heavy Counties Supported Sanders and Warren

Iowa’s counties vary drastically in terms of population size and demographics; places like Story County and Johnson County, for example, can have two to three times the proportion of youth compared to some of the more rural and exurban counties in the state. To examine what candidate support looked like in areas of the state with different demographic makeups, we used Census data to divide counties into three groups based on the percentage of young people among the county’s total population. That allowed us to categorize each county as having a “Low”, “Medium”, or “High” youth population relative to other counties within the state. (We used a similar method to look at key states in the 2018 midterm elections.) 

Our analysis finds that counties with “high” relative youth density strongly boosted Sanders’ and Warren’s performances in the state, while Biden struggled. Buttigieg, however, received consistent support in counties with low, medium, and high youth density, indicating that he appealed similarly to Iowa voters across multiple age groups. It’s important to remember that average candidate support within a group of counties is different from overall candidate support in the state because the number of people in each county varies widely.There are also many reasons why certain counties would more heavily support one candidate over another, such as other demographic differences, so we are examining the proportion of youth as one of many possible salient factors.

To do this, we examined the percentage of state delegate equivalents (SDEs) won by each candidate in a county (as aggregated by the state party) to determine average support for each of the four top candidates in Iowa: Buttigieg, Sanders, Warren, and Biden. While SDEs are the metric by which the Iowa Democratic Party traditionally declares a winner in the caucuses, SDEs are not perfectly proportionate to the final votes per candidate statewide. In counties with “low” and “medium” proportions of youth, Buttigieg earned a clear lead in SDEs over the rest of the field, with Sanders trailing in the low-youth counties by a margin of 10 percentage points and in the medium-youth counties by 5 percentage points. By contrast, In low- and medium-youth counties, Biden enjoyed the second-highest level of support despite his fourth-place finish overall. But in counties with high proportions of youth, Biden fell to fourth place among the candidates, whereas Sanders narrowed the gap to less than one percentage point of Buttigieg.

Sanders’ strength in the high-youth counties was instrumental in narrowing Buttigieg’s SDE lead, as it compensated for Sanders’ weaker performance in suburban counties with fewer SDEs in play. As one example of how high-youth parts of the state had an outsize influence on the caucuses, Warren and Sanders finished in the top two in both Johnson County and Story County, which are home to the University of Iowa and Iowa State University, respectively, and thus have the two highest youth shares of any county in the state. In contrast, whereas Warren and Sanders each won more than 53 SDEs and 32% of the total share in Johnson County, in neighboring Cedar County Pete Buttigieg’s victory earned him only 3 SDEs out of the 12 available, highlighting the power of youth-dense areas of the state.

As the 2020 Democratic primaries continue in New Hampshire and beyond, we will continue to offer in-depth analysis of how young people are shaping the nominating contests.


Authors: Kristian Lundberg, Rey Junco, Alberto Medina